The present invention relates to conical crushers designed for the comminution of rocks and/or other mineral materials, and specifically relates to the relative crushing surface configurations of a head mantle and a bowl liner of such a crusher.
Conical crushers are provided in a variety of operational modifications, but most such crushers include a fixed lower frame defining a space in which a conical head is caused to gyrate about a vertical axis, and a movable upper frame having a bowl with a bowl liner which defines a negative concave, the bowl and the head disposed relative to each other to define a crushing cavity. The head usually includes a head mantle which is replaceable, and the bowl liner is also replaceable. Feed material introduced at an upper end of the machine falls into the crushing cavity where it is comminuted by the action of the head mantle against the bowl liner.
In conventional crushers, the conical head mantle has an exterior crushing surface which is generally concave in cross-section, while an exterior crushing surface of the bowl liner is generally convex in cross-section. These working surfaces of the mantle and bowl liner often form a downwardly tapering crushing cavity which is generally V-shaped in cross-section. Such an arrangement is disclosed in U.S. Pat. No. 3,666,188. The width of this cavity at the crusher setting, or narrowest point between the bowl liner and the head, determines the maximum particle size in the crushed material, and the nip angle of the V-shaped cavity is important to the throughput or production of the machine. If the nip angle is too large, the resistance to downfeeding of larger particles will be unacceptably great, and moreover, these larger particles even show a tendency towards moving upwardly and blocking the crushing cavity.
Another design feature of conventional conical crushers is the creation of a parallel zone at the lower end of the crushing cavity which is defined by generally parallel opposing faces of the head mantle and bowl liner. The purpose of the parallel zone is to maximize the reduction of feed material by forcing the material to be comminuted between the head mantle and the bowl liner a minimum of one more time at the minimum crusher setting before the material is discharged from the crusher.
Although maximum reduction is desirable in mining applications, it is undesirable in the production of aggregate material for use as base material, concrete stone and asphalt fillers, due to the production of excessive amounts of fines and dust. These latter byproducts are considered waste material, for they have little, if any commercial value, are difficult to dispose of, and may be hazardous to health or to the environment. Users of conventional conical crushers for the production of aggregate have increasingly demanded increased yields of Number 8 stone (nominally 3/8 inch by 8 mesh crushed material) and a decrease in the amount of minus 200 mesh waste material.
Attempts have been made to alter the shape of the relative exterior crushing surfaces of the head mantle and the bowl liner to achieve certain specified product shapes and/or production volumes. U.K. published application No. 2,123,314 discloses opposing mantle and bowl liner surfaces configured so that the generally parallel zone between the upper portions of these components of the crushing cavity will remain constant as the position of the head is axially adjusted. However, the above-identified crusher, as well as the majority of conventional conical crushers, still retains the parallel zone at the lower end of the crusher cavity, where it is believed much of the waste material is generated.
Another design parameter which influences the shape of crushing cavities is that, through use, the configurations of the opposing crushing surfaces of the head mantle and bowl liner will erode. This erosion is usually accommodated for by adjusting the position of the bowl relative to the head; however, such erosion and adjustment of eroded crushing surfaces often changes the geometry of the original crushing cavity. Consequently, the shape of the crushed product may be changed, and/or the total volume of material produced by the crusher may be reduced.
Thus, an object of the present invention is to provide a conical crusher which is designed to achieve high yields of aggregate type material while minimizing waste material.
Another object of the present invention is to provide a conical crusher in which feed material flows generally uniformly through the crusher cavity to promote interparticle comminution and improve the shape of the discharged particles.
Still another object of the present invention is to provide a conical crusher in which the crushing surfaces of the head mantle and the bowl liner are configured for maximization of yield and minimization of waste despite the erosion of the crushing surfaces.